PCF8813 View Datasheet(PDF) - Philips Electronics
Part Name
Description
MFG CO.
'PCF8813' PDF : 72 Pages View PDF
Philips Semiconductors
(67 + 1) × 102 pixels matrix LCD driver
Product specification
PCF8813
The generated voltage at VLCD is dependent on the
temperature, programmed temperature coefficient (TC)
and the programmed voltage at the reference temperature
(TCUT):
VLCD = [a + VOP × b] × [1 + TC × (T – TCUT)]
TCUT and voltages a and b for each temperature
coefficient are quoted in Table 17. The maximum voltage
that can be generated is dependent on the voltage of VDD2
and the display load current.
As the programming range for the internally generated
VLCD allows values above the maximum allowed VLCD,
the user must ensure that while setting the VPR
register and selecting the temperature compensation,
under all conditions and including all tolerances the
VLCD maximum limit of 9.0 V will never be exceeded.
For a particular liquid crystal, the optimum VLCD can be
calculated for a given multiplex rate. For 1 : 68, the
optimum operating voltage of the liquid crystal can be
calculated as;
VLCD = -----2-----×1-----+--1-----–--6----8------1--6------8------- × Vth = 6.98 × Vth
where Vth is the threshold voltage of the liquid crystal used.
Table 17 Parameters of HV generator programming (typical values)
Nominal temperature = 27 °C; temperature coefficients calculated at nominal VLCD = 8.6 V.
SYMBOL
PARAMETER
TC0
TC1
TC2
TC3
a
b
TCUT
TC
first level VLCD voltage
4.57
programmed voltage step 30.5
reference temperature
27
temperature coefficient
0.00
4.27
28.5
27
−0.25
4.01
26.7
27
−0.48
3.84
25.6
27
−0.64
UNIT
V
mV
°C
mV/K
handbook, full pagewidth
V LCD
MGT847
b
a
00 01 02 03 04 05 06 . . .
. . . FD FE FF
V OP
If VPR[6:0] is set to zero, the charge pump is turned off.
Depending on VPR restrictions defined in Table 17 and depending on VCAL, not all VOP[7:0] values can be selected.
Fig.35 VLCD as a function of VOP[7:0] programming.
2004 Mar 05
37
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